Disk drives using various kinds of disks, such as optical disks, magneto-optical disks, flexible magnetic-recording disks and similar data-storage disks are known in the art. In particular, hard-disk drives (HDDs) have been widely used as indispensable data-storage devices for contemporary computer systems. Moreover, HDDs have found widespread application to motion picture recording and reproducing apparatuses, car navigation systems, cellular phones, removable memories used in digital cameras and similar devices, in addition to the computers, because of their outstanding data-storage characteristics.
Magnetic-recording disks used in an HDD include multiple concentric data tracks and multiple servo sectors disposed discretely in the circumferential direction of each magnetic-recording disk. User data are recorded in units of data sectors and data sectors are recorded between servo sectors. A rotary actuator moves a head-slider in proximity to the recording surface of a spinning magnetic-recording disk. A magnetic-recording head of a head-slider accesses designated data sectors in accordance with positional data indicated by servo sectors to write data to, and read data from, the data sectors.
Higher recording density of a HDD is attended by larger storage capacity; and, servo track density increases with data track density. Thus, servo control of a magnetic-recording head in a HDD is more susceptible to external vibrations. External vibrations could cause a reduction in positional control accuracy, a reduction in performance and data corruption. A method to increase the vibration resistance of servo control is to increase the servo sampling frequency. However, processing power increases with increasing servo sampling frequency. Additionally, since many resonance modes exist at high frequencies, the servo frequency has become difficult to increase.
Engineers and scientists engaged in HDD manufacturing and development are interested in the methods and systems for servo writing HDDs that meet the rising demands of the marketplace for increased data-storage capacity, performance, and reliability.